Liquid crystal display device

ABSTRACT

The present invention provides a liquid crystal display device which includes a pixel electrode and a counter electrode in a pixel formed on a surface of a substrate which faces liquid crystal, the counter electrode is formed below an insulation film, and the pixel electrode is formed above the insulation film, wherein the counter electrode is formed over a whole area of a center except for a slight periphery of at least the pixel, the pixel electrode is constituted of separate pixel electrodes to which a video signal which is supplied to the pixel is inputted through the separate switching elements at the same timing, and the separate pixel electrodes are respectively formed of a plurality of electrodes and the respective electrodes are alternately arranged.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device which forms pixelelectrodes and counter electrodes on a liquid crystal surface side ofone substrate out of respective substrates which are arranged to faceeach other with liquid crystal therebetween.

2. Description of the Related Art

This type of liquid crystal display device is configured to control aquantity of light which passes through a region defined between pixelelectrodes and counter electrodes by driving liquid crystal to which anelectric field generated between respective electrodes is applied.

Such a liquid crystal display device has been known as a display devicewhich exhibits excellent property in a so-called wide viewing angle,wherein the display is not changed even when viewed from the obliquedirection with respect to a display surface.

Heretofore, the pixel electrodes and the counter electrodes are formedof a conductive layer which prevents light from passing through theseelectrodes.

However, recently, there has been known a liquid crystal display devicehaving the constitution in which counter electrodes formed of atransparent electrode are formed over the whole area of a pixel regionexcept for a periphery of the pixel region, and strip-like orcomb-teeth-shaped pixel electrodes are arranged over the counterelectrodes by way of an insulation film in a state that the transparentelectrodes extend in one direction and are arranged in parallel in thedirection which intersects one direction.

The liquid crystal display device having such a constitution generatesan electric field which is substantially parallel to substrates betweenthe pixel electrode and the counter electrode and hence, the liquidcrystal display device can largely enhance a so-called numericalaperture while still ensuring the excellent wide viewing angle property.

Further, in such a constitution, when short-circuiting arises betweenthe pixel electrode and the counter electrode which is arranged belowthe pixel electrode by way of an insulation film through a pin hole, aso-called point defect arises. As a liquid crystal display device whichcan overcome such a point defect, there has been known a liquid crystaldisplay device disclosed in Japanese Patent Laid Open 2005-148534 whichis a patent application filed prior to this application filed by thesame applicant. Family of this application is co-pending in the U.S.application Ser. No. 10/977,934.

In this literature, there is disclosed the constitution in which twopixel electrodes which are physically separated from each other areformed on the pixel region, and a video signal is supplied to theserespective pixel electrodes through two respective thin film transistorswhich are turned on simultaneously in response to a scanning signal froma gate signal line.

Such a liquid crystal display device obtains an advantageous effect thateven when one pixel electrode is short-circuited with the counterelectrode, another pixel electrode still performs a function thereof andhence, a point defect does not occur.

SUMMARY OF THE INVENTION

However, the liquid crystal display device having such a constitution isconfigured such that the respective pixel electrodes are formed inrespective regions which are defined by dividing the pixel with animaginary line segment which passes the center of the pixel.

Accordingly, the liquid crystal display device is obliged to abandon adisplay in one region where the short-circuited pixel electrode isformed and hence, the brightness in the pixel inevitably is halved.

The present invention has been made under such circumstances and it isone advantage of the present invention to provide a liquid crystaldisplay device which can prevent the brightness in a pixel from beinghalved even when short-circuiting arises between a pixel electrode and acounter electrode.

To briefly explain the summary of typical inventions among theinventions disclosed in this specification, they are as follows.

(1)

A liquid crystal display device according to the present inventionincludes, for example, a pixel electrode and a counter electrode in apixel formed on a surface of a substrate which faces liquid crystal, thecounter electrode is formed below an insulation film, and the pixelelectrode is formed above the insulation film, wherein

the pixel electrode is constituted of separate pixel electrodes whichare formed on the counter electrode in an overlapped manner to which avideo signal which is supplied to the pixel is inputted to the separatepixel electrodes through separate switching elements at the same timing,and the separate pixel electrodes are respectively formed of a pluralityof electrodes and the respective electrodes are alternately arranged.

(2)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (1), characterized inthat the separate switching elements are turned on in response to asignal from a common gate signal line.

(3)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (1), characterized inthat one pixel electrode out of the separate pixel electrode has acomb-teeth-shaped pattern in which a conductive body to which respectiveelectrodes are commonly connected is arranged close to one of drainsignal lines which are arranged to sandwich the pixels, and anotherpixel electrode out of the separate pixel electrode has acomb-teeth-shaped pattern in which a conductive body to which respectiveelectrodes are commonly connected is arranged close to another drainsignal line.

(4)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (1), characterized inthat the counter electrode of each pixel is electrically connected withthe counter electrode of another pixel which is arranged close to eachpixel with a gate signal line arranged therebetween through a conducivelayer which is formed on an insulation film which is formed in a statethat the insulation film also covers the gate signal line.

(5)

A liquid crystal display device according to the present inventionincludes, for example, two neighboring thin film transistors in eachpixel, wherein

semiconductor layers of the respective thin film transistors are formedin common, on upper surfaces of the semiconductor layers, respectivedrain electrodes of the respective thin film transistors are formed in astrip shape, are curved and are formed in an semicircular shape having acenter thereof on distal ends of source electrodes which constitutepairs with the drain electrodes, and

the drain electrode of one thin film transistor is physically commonlyconnected with the drain electrode of another thin film transistor at aposition where the drain electrodes are arranged close to each other,and a width of a commonly connected portion is equal to a width ofportions other than the commonly connected portion.

(6)

A liquid crystal display device according to the present inventionincludes, for example, a pixel electrode and a counter electrode in apixel formed on a surface of a substrate which faces liquid crystal, thecounter electrode is formed below an insulation film, and the pixelelectrode is formed above the insulation film, wherein

the counter electrode is formed over a whole area of a center except fora slight periphery of at least the pixel, the pixel electrode isconstituted of separate pixel electrodes to which a video signal whichis supplied to the pixel is inputted through separate thin filmtransistors at the same timing,

the separate pixel electrodes are respectively formed of a plurality ofelectrodes and the electrodes are alternately arranged, and

the separate thin film transistors have semiconductor layers in common,on upper surfaces of the semiconductor layers, respective drainelectrodes of the respective thin film transistors are formed in a stripshape, are curved and are formed in an semicircular shape having acenter thereof on distal end portions of source electrodes whichconstitute pairs with the drain electrodes,

the drain electrode of one thin film transistor is physically commonlyconnected with the drain electrode of another thin film transistor at aposition where the drain electrodes are arranged close to each other,and a width of a commonly connected portion is equal to a width ofportions other than the commonly connected portion.

(7)

A liquid crystal display device according to the present inventionincludes, for example, a first substrate and a second substrate whichare arranged to face each other with liquid crystal therebetween, aplurality of gate signal lines and a plurality of drain signal lineswhich are formed on the first substrate, pixels which are formed asregions which are surrounded by the plurality of gate signal lines andthe plurality of drain signal lines, counter electrodes formed on thepixels, an insulation film formed above the counter electrodes, andpixel electrodes formed above the insulation film, wherein

the pixel electrode includes a first pixel electrode and a second pixelelectrode which are overlapped to the counter electrode in plane, thefirst pixel electrode and the second pixel electrode are electricallyconnected with the same drain signal line through separate switchingelements, the first pixel electrodes and the second pixel electrodesrespectively include a plurality of electrodes, and the electrodes whichbelong to the first pixel electrode and the electrodes which belong tothe second pixel electrode are alternately arranged.

(8)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (7), characterized inthat the separate switching elements are controlled by the same gatesignal line.

(9)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (7), characterized inthat the first pixel electrode has a comb-teeth-shaped pattern in whicha conductive body to which the plurality of electrodes are commonlyconnected is arranged close to one drain signal line of the pixel, andthe second pixel electrode has a comb-teeth-shaped pattern in which aconductive body to which the plurality of electrodes are commonlyconnected is arranged close to another drain signal line of the pixel.

(10)

A liquid crystal display device according to the present invention is,for example, on the premise of the constitution (7), characterized inthat the counter electrode of each pixel is electrically connected withthe counter electrode of another pixel which is arranged close to eachpixel with a gate signal line arranged therebetween through a conducivelayer which is formed on an insulation film which is formed in a statethat the insulation film also covers the gate signal line.

(11)

A liquid crystal display device according to the present inventionincludes, for example, on the premise of the constitution (7) twoneighboring thin film transistors in each pixel, wherein semiconductorlayers of the respective thin film transistors are formed in common, onupper surfaces of the semiconductor layers, respective drain electrodesof the respective thin film transistors are formed in a strip shape, arecurved and are formed in an semicircular shape having a center thereofon distal ends of source electrodes which constitute pairs with thedrain electrodes, and the drain electrode of one thin film transistor isphysically commonly connected with the drain electrode of another thinfilm transistor at a position where the drain electrodes are arrangedclose to each other.

Here, the present invention is not limited to the above-mentionedconstitutions and various modifications are conceivable withoutdeparting from the technical concept of the present invention.

According to the liquid crystal display device having suchconstitutions, even when short-circuiting with the counter electrodearises in one of pixel electrodes which are connected to respective thinfilm transistors, the pixel electrode is converted to the counterelectrode which contributes to the display in the pixel.

This is because that the respective electrodes which constitute onepixel electrode and the respective electrodes which constitute anotherpixel electrode are alternately (in a nest-shape) arranged and therespective electrodes of the converted pixel electrode generate anelectric field between the respective electrodes of the converted pixelelectrode and the respective electrodes of another pixel electrode whichis arranged close to the electrodes of the converted pixel electrode.

In this case, when the display is performed only based on the electricfield, although the brightness is halved before and after theshort-circuiting, there is no change before and after theshort-circuiting with respect to a phenomenon that the original counterelectrode which is arrange below the insulation film also contribute tothe display.

This is because that, with respect to the respective electrodes ofanother pixel electrode, the electric field (edge electric field) isgenerated between the respective electrodes of another electrode and thecounter electrode mainly in the peripheries of the respective electrodesand this electric field also sufficiently contributes to the display.

Accordingly, even when the short-circuiting arises between the pixelelectrode and the counter electrode, it is possible to drive the liquidcrystal display device without halving the brightness in the pixel.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view showing one embodiment of the constitution of apixel of a liquid crystal display device according to the presentinvention;

FIG. 2 is a cross-sectional view taken along a line I(a)-I(b) in FIG. 1;

FIG. 3 is an explanatory view showing an advantageous effect of theliquid crystal display device according to the present invention;

FIG. 4 is a cross-sectional view taken along a line I(a)-I(b) in FIG. 3;

FIG. 5 is a plan view showing one embodiment of the constitution of thepixel of the liquid crystal display device according to the presentinvention;

FIG. 6 is a plan view showing one embodiment of the constitution of thepixel of the liquid crystal display device according to the presentinvention;

FIG. 7 is a plan view showing one embodiment of the constitution of thepixel of the liquid crystal display device according to the presentinvention; and

FIG. 8 is a view showing an equivalent circuit of one embodiment of adisplay part of the liquid crystal display device according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of a liquid crystal display device accordingto the present invention is explained in conjunction with drawings.

FIG. 8 is an equivalent circuit diagram showing one embodiment of theliquid crystal display device according to the present invention. Theequivalent circuit shown in FIG. 8 is an equivalent circuit which isformed on a liquid-crystal-side surface of one substrate out ofrespective substrates which are arranged to face each other with liquidcrystal therebetween.

First of all, on the above-mentioned substrate surface, gate signallines GL which extend in the x direction and are arranged in parallel inthe y direction are formed and, at the same time, drain signal lines DLwhich extend in the y direction and are arranged in parallel in the xdirection are formed. A portion surrounded by the gate signal lines GLand the drain signal lines DL forms a pixel region where a pixel isformed, and a liquid crystal display part AR is constituted of a mass ofthe pixel regions.

In the inside of a group of pixel regions which is constituted ofrespective pixel regions which are arranged in parallel in the xdirection in the drawing, a reference signal line CL which extends inthe x direction is formed, and the reference signal line CL is connectedwith reference signal lines CL which are formed in the inside of othergroups of pixel regions corresponding to these reference signal linesoutside the liquid crystal display part AR.

Each pixel region includes two thin film transistors TFT1, TFT2 whichare turned on in response to a signal (scanning signal) from the gatesignal line GL. When one thin film transistor TFT1 is turned on, asignal from one drain signal line DL (left side in the drawing) out of apair of drain signal lines DL which sandwich the pixel region issupplied to a pixel electrode PX1. In the same manner, when another thinfilm transistor TFT2 is turned on, a signal from the above-mentioneddrain signal line DL is supplied to a pixel electrode PX2.

Here, the pixel electrode PX1 and the pixel electrode PX2 arerespectively independently formed and these pixel electrodes generateelectric fields between these electrodes and a common counter electrodeCT which is connected to the above-mentioned reference signal line CL.The above-mentioned constitution in which each pixel region includes twothin film transistors TFT1, TFT2 and two pixel electrodes PX1, PX2 whichare respectively connected to these respective thin film transistorsTFT1, TFT2 is provided for preventing a phenomenon that whenshort-circuiting arises between one of the pixel electrodes PX1, PX2 andthe counter electrode CT in the inside of the pixel, damages which reacha so-called point defect arises. This provision is explained in detaillater.

Here, the above-mentioned gate signal lines GL have one ends thereofconnected to a scanning signal drive circuit V and a scanning signal issequentially scanned and supplied to respective gate signal lines GL bythe scanning signal drive circuit V. Further, the above-mentioned drainsignal lines DL have one ends thereof connected to a video signal drivecircuit He and a video signal is supplied to the respective drain signallines DL by the video signal drive circuit He.

That is, a group of pixels (line) which is constituted of the respectivepixels arranged in parallel in the x direction in the drawing is drivensuch that group of pixels is sequentially selected by the scanningsignal, and the video signal is supplied to the respective pixels of theline in conformity with the selection timing.

FIG. 1 is a plan view of the specific constitution which shows theabove-mentioned constitution in the pixel. Further, FIG. 2 shows a crosssection taken along a line I(a)-I(b) in FIG. 1.

On a main surface of the substrate SUB1, the counter electrode CT isformed using a light transmitting material such as ITO (Indium TinOxide), for example.

The pixel region is constituted of a region surrounded by gate signallines GL and the drain signal lines DL described later, while thecounter electrode CT is formed over the whole area of a center portionexcept for a slight periphery of the region.

Further, the gate signal lines GL and the reference signal lines CL areformed. These gate signal lines GL and reference signal lines CL are,for example, formed in the same step and hence, the gate signal lines GLand the reference signal lines CL are constituted of a same material.

Here, the reference signal line CL is formed close to and adjacent toone gate signal line GL out of the respective gate signal lines GL whichsurround the pixel region and, at the same time, the reference signalline CL is directly overlapped to the counter electrode CT whereby thereference signal line CL is electrically connected with the counterelectrode CT.

Further, over a whole area of the main surface of the substrate SUB1, aninsulation film GI is formed in a state that the insulation film GIcovers the above-mentioned gate signal lines GL and the like. Theinsulation film GI functions as the gate insulation film for the thinfilm transistor TFT described later and, at the same time, functions asan interlayer insulation film.

On a portion of a region of an upper surface of the insulation film GIwhich is overlapped to the above-mentioned gate signal line GL, asemiconductor layer AS is formed. The semiconductor layer AS is formedof a first semiconductor layer AS1 and a second semiconductor layer AS2.This constitution is provided for forming the first thin film transistorTFT1 and the second thin film transistor TFT2 on portions where therespective semiconductor layers are formed.

In this case, the respective semiconductor layers AS1, AS2 are arrangedto approach the left side of the pixel region, that is, the drain signalline DL side for introducing the video signal to the pixel.

By forming a pair of opposing electrodes (source and drain electrodes)on an upper surface of each semiconductor layer AS1, AS2, a transistorhaving the inverse staggered MIS structure which adopts theabove-mentioned gate signal line GL as a gate electrode is formed,wherein the electrodes are simultaneously formed with the formation ofthe drain signal line DL.

That is, a part of the drain signal line DL which is positioned on theleft side of the pixel region includes a portion which extends inparallel to the gate signal line GL, and the extending portion is bentand bent portions get over the semiconductor layers AS1, AS2 from oneside thereof which are respectively arranged close to the extendingportion thus forming drain electrodes SD11, SD21. Further, on a surfaceof each semiconductor layer AS1, AS2, source electrodes SD12, SD22 areformed in a spaced-apart manner from the respective drain electrodesSD11, SD21 by a channel length. Here, the source electrodes SD12, SD22are formed in a state that the source electrodes SD12, SD22 includeextending portions which are slightly extended toward the pixel regionside from the surfaces of the respective semiconductor layers AS1, AS2.These extending portions are provided to form portions which establishthe connection with the pixel electrodes PX1, PX2 described later.

Further, over a whole area of the surface of the substrate SUB1, aprotective film PAS is formed in a state that the protective film PASalso covers the above-mentioned drain signal lines DL. The protectivefilm PAS has a function of obviating the direct contact of theabove-mentioned thin film transistors TFT1, TFT2 with liquid crystal LCdescribed later, wherein a material of the protective film PAS is aninorganic material, an organic material, a stacked body of an inorganicmaterial and an organic material or the like.

The pixel electrodes PX is formed on a surface of the protective filmPAS. The pixel electrode PX is formed in the inside of a region wherethe counter electrode CT is formed. Due to such a constitution, thepixel electrode PX is overlapped to the counter electrode CT in a statethat the insulation film GI and the protective film PAS are interposedtherebetween.

The pixel electrode PX is constituted of a first pixel electrode PX1 anda second pixel electrode PX2. The first pixel electrode PX1 has aportion thereof electrically connected with the extending portion of thesource electrode SD12 of the above-mentioned thin film transistor TFT1through a contact hole CN1 which is preliminarily formed in theabove-mentioned protective film PAS below the first pixel electrode PX1.In the same manner, the second pixel electrode PX2 has a portion thereofelectrically connected with the extending portion of the sourceelectrode SD12 of the above-mentioned thin film transistor TFT2 througha contact hole CN2 which is preliminarily formed in the above-mentionedprotective film PAS below the second pixel electrode PX2.

The first pixel electrode PX1 and the second pixel electrode PX2 are,respectively, constituted of a group of electrodes formed of a pluralityof electrodes which are extended substantially in the x direction andare arranged in parallel in the y direction, wherein the electrodes ofthe first pixel electrode PX1 and the electrodes of the second pixelelectrode PX2 are respectively alternately arranged.

Further, in the first pixel electrode PX1, the respective electrodes areintegrally formed with a conductive layer PD1 which is formed close toand in parallel to the drain signal line DL which supplies the videosignal to the pixel thus forming a comb-teeth-shaped pattern. Also inthe second pixel electrode PX2, the respective electrodes are integrallyformed with a conductive layer PD2 which is formed close to and inparallel to the drain signal line DL which is different from theabove-mentioned drain signal line DL and sandwiches the pixeltherebetween thus forming a comb-teeth-shaped pattern.

Further, a conductive member SE which is formed simultaneously at themanufacture of the pixel electrode PX is formed in a state that theconductive member SE traverses a portion of the gate signal line GL. Theconductive member SE is formed at a position close to another drainsignal line DL different from the drain signal line DL which suppliesthe video signal to the pixel through the thin film transistor TFT. Byselecting the position which is relatively spaced-apart from the thinfilm transistor TFT, it is possible to sufficiently avoid the contact ofthe conductive member SE with the thin film transistor TFT.

One end of the conductive member SE in the pixel region is electricallyconnected with the reference electrode CL through a contact hole CN4which penetrates the protective film PAS and the insulation film GIbelow the conductive member SE, while another end of the conductivemember SE in another neighboring pixel region is electrically connectedwith the counter electrode CT in another pixel region through a contacthole CN3 which penetrates the protective film PAS and the insulationfilm GI below the conductive member SE.

In the display part, with respect to the respective counter electrodesCT which are physically separated from each other and are scattered forrespective pixels, the counter electrode CT of each pixel is connectedwith the counter electrode CT of other neighboring pixel in the xdirection using the reference signal line DL and is connected with thecounter electrode CT of other neighboring pixel in the y direction usingthe above-mentioned conductive member SE and hence, it is possible toobtain an advantageous effect that the supply of the reference signalcan be performed without giving rise to a distortion of waveforms ineach pixel.

An orientation film ORI1 is formed over the whole area of the surface ofthe substrate SUB1 in a state that the orientation film ORI1 also coversthe pixel electrodes PX and the like. The orientation film ORI1 has afunction of initially orienting molecules of the liquid crystal LC whichis brought into contact with the orientation film ORI1.

Here, on a liquid-crystal LC-side surface of another substrate SUB2which is arranged over one substrate SUB1 by way of liquid crystal LC, ablack matrix BM which is formed to define the pixel from the neighboringother pixels, a color filter FIL which is formed to allow the pixel tobe allocated to one color out of three primary colors for color display,a leveling film OC which is formed for leveling a surface of the colorfilter FIL, and an orientation film ORI2 which is formed for initiallyorienting the molecules of the liquid crystal LC are formed.

Through the thin film transistors TFT1, TFT2 which are simultaneouslyturned on in response to the supply of the scanning signal from the gatesignal line GL, the video signal from the drain signal line DL issupplied to the pixel electrodes PX1, PX2 respectively. On the otherhand, a signal which becomes the reference with respect to the videosignal is supplied to the counter electrode CT through the referencesignal line CL.

Accordingly, as shown in FIG. 2, electric fields (lines of electricforces) E are generated between the pixel electrode PX (PX1, PX2) andthe counter electrode CT thus activating the behavior of the moleculesof the liquid crystal LC.

In this case, the electric fields E are generated substantiallyvertically with respect to the counter electrode CT at a periphery (edgeportion) of the counter electrode CT, and are generated substantiallyparallel to the substrate SUB1 over the whole electrode CT and bothelectric fields E contribute to the behavior of molecules of the liquidcrystal LC.

FIG. 3 is an explanatory view showing an advantageous effect of theliquid crystal display device having the above-mentioned constitutionand corresponds to FIG. 1.

Assume that, as shown in FIG. 3, a portion of the pixel electrode PX(the portion indicating the pixel electrode PX2 in the drawing) isshort-circuited with the counter electrode CT through a pin hole whichis undesirably formed in the protective film PAS and the insulation filmGI below the pixel electrode PX2. The formation of the pin hole in theprotective film PAS and the insulation film GI is a phenomenon whichoften occurs due to the presence of a foreign substance, for example,during the manufacture of the liquid crystal display device.

Here, the short-circuiting between the pixel electrode PX2 and thecounter electrode CT due to the above-mentioned pin hole is shown inFIG. 4 which is a cross-sectional view taken along a line I(a)-I(b) inFIG. 3.

When such short-circuiting arises, the pixel electrode PX2 has the samepotential as the counter electrode CT and hence, a function of the pixelelectrode PX2 is damaged. However, the pixel electrode PX2 is convertedto the counter electrode and possesses a function of the counterelectrode and hence, an electric field is generated between theconverted counter electrode and the pixel electrode PX1 which isarranged close to the converted counter electrode and the electric fieldcontributes to the display.

Further, the function of the pixel electrode PX1 after short-circuitingis equal to the function of the pixel electrode PX1 before theshort-circuiting and still generates the electric fields between thepixel electrode PX1 and the original counter electrode CT which isarranged below the protective film PAS and the insulation film GI thuscontributing to the display.

Due to such a constitution, even when the short-circuiting arisesbetween the pixel electrode and the counter electrode, it is possible todrive the liquid crystal display device without decreasing thebrightness of the pixel to one half of the original brightness.

FIG. 5 is a plan view of another embodiment of the pixel of the liquidcrystal display device according to the present invention andcorresponds to FIG. 1.

The constitution which makes this embodiment different from theembodiment shown in FIG. 1 lies in, first of all, the thin filmtransistors TFT1 and TFT2.

Respective drain electrodes SD11, SD21 of thin film transistors TFT1,TFT2 which are arranged close to a gate signal line GL are formed in apattern in which the drain electrodes SD11, SD21 surround distal ends ofsource electrodes SD12, SD22 of the thin film transistors TFT1, TFT2.

Here, the distal ends of the source electrodes SD12, SD22 are endportions thereof on a side opposite to a side which is connected withcorresponding pixel electrodes PX1, PX2 and are portions whichsubstantially function as the source electrodes SD12, SD22 of the thinfilm transistors TFT1, TFT2.

That is, the drain electrode SD11 is formed in a strip shape and iscurved to form a semicircular shape having a center thereof at theabove-mentioned distal end portion of the source electrode SD12 whichconstitutes a pair of electrodes with the drain electrode SD11. In thesame manner, the drain electrode SD21 is also formed in a strip shapeand is curved to form a semicircular shape having a center thereof atthe above-mentioned distal end portion of the source electrode SD22which constitutes a pair of electrodes with the drain electrode SD21.

Further, these drain electrode SD11 and drain electrode SD21 haveneighboring portions thereof physically connected with each other,wherein a width of the connecting portion is set equal to a width ofthese electrodes other than the connecting portion. Accordingly, thedrain electrode SD11 and the drain electrode SD21 are formed in asubstantially “W”-shaped pattern in which the drain electrode SD11 andthe drain electrode SD21 respectively have smooth arcuate portions.

The formation of the drain electrode SD11 and the drain electrode SD21in a state that the drain electrodes SD11, SD21 surround the sourceelectrodes SD12, SD22 which constitute pairs with the drain electrodesSD11, SD21 is provided for increasing channel widths of the respectivethin film transistors TFT1, TFT2. To set channel lengths uniform alongthe channel width direction, the distal end portions of the sourceelectrodes SD12, SD22 are formed in an arcuate shape where corners arerounded. Such formation of the distal end portions of the sourceelectrodes SD12, SD22 is provided for aligning the curvature of distalend portions of the source electrodes SD12, SD22 with the curvature ofinner periphery (a peripheral surface which faces the source electrodesSD12, SD22) of the drain electrode SD11 and the drain electrode SD21.

Due to such a constitution, it is possible to ensure large channelwidths of both thin film transistors TFT1, TFT2 and, at the same time,it is possible to arrange these thin film transistors TFT1, TFT2 asclose as possible. This is because that, as described above, the widthof the connecting portion between the drain electrode SD11 and the drainelectrode SD21 is set equal to the widths of the drain electrode SD11and the drain electrode SD21 other than the connecting portion.

In the case of this embodiment, as described above, the conductivemember SE which is provided for connecting the counter electrodes CT ofthe neighboring respective pixels with the gate signal line GLtherebetween is arranged and hence, it is possible to ensure thesufficient distance between the above-mentioned thin film transistorsTFT1, TFT2 thus giving rise to an advantageous effect that theshort-circuiting between the thin film transistors TFT1, TFT2 can besufficiently avoided.

Here, although the semiconductor layers AS of the thin film transistorsTFT1, TFT2 may be formed in common and a shape of the semiconductorlayers AS may be a rectangular shape, in FIG. 5, the semiconductor layerAS is configured such that other sides except for one side of therectangular shape thereof conform to outer periphery of the drainelectrode SD11, SD21.

Further, the pixel electrode PX1 which is connected to the sourceelectrode SD12 of the thin film transistor TFT1 is configured to avoid astate that a connecting portion thereof faces the pixel electrode PX2which is arranged close to the connecting portion in the y direction.This constitution differs from the constitution of the case shown inFIG. 1 at the same position. That is, this constitution is resulted fromthe arrangement in which the respective thin film transistors TFT1, TFT2can be arranged close to each other.

Here, the pixel electrode PX2 which is arranged close to the connectingportion in the y direction is configured to project toward the thin filmtransistors TFT1 side than the branched portion necessary for theconnection with the source electrode SD22 in the longitudinal direction.This constitution is adopted to enlarge the region which functions asthe pixel.

Accordingly, as shown in FIG. 6 which shows another embodimentcorresponding to FIG. 5, it is needless to say that the formation of theprojecting portion is not always necessary.

FIG. 7 is a view showing another modification of the pattern of thepixel electrode PX1, PX2. Using an imaginary line segment which runs inthe x direction in the drawing at the center of the pixel region, thepattern of the pixel electrode PX1, PX2 on the side where the thin filmtransistors TFT1, TFT2 are formed is substantially equal to the patternshown in FIG. 6, fore example. On the other hand, with respect to thispattern, the upper-side pattern in the drawing has the line symmetryrelationship using the above-mentioned imaginary line segment.

Due to such a constitution, it is possible to make an angle of runningdirection of the electrodes of the respective pixel electrodes PX1, PX2different from each other between the upper side and the lower side inthe drawing thus capable of adopting the so-called multi-domainstructure.

The above-mentioned respective embodiments may be used in an independentmanner from each other or in combination. This is because that therespective advantageous effects may be obtained singly orsynergistically.

1. A liquid crystal display device which includes a pixel electrode anda counter electrode in a pixel formed on a surface of a substrate whichfaces liquid crystal, the counter electrode is formed below aninsulation film, and the pixel electrode is formed above the insulationfilm, wherein the pixel electrode is constituted of separate pixelelectrodes which are formed on the counter electrode in an overlappedmanner to which a video signal which is supplied to the pixel isinputted to the separate pixel electrodes through separate switchingelements at the same timing, and the separate pixel electrodes arerespectively formed of a plurality of electrodes and the respectiveelectrodes are alternately arranged.
 2. A liquid crystal display deviceaccording to claim 1, wherein the separate switching elements are turnedon in response to a signal from a common gate signal line.
 3. A liquidcrystal display device according to claim 1, wherein one pixel electrodeout of the separate pixel electrode has a comb-teeth-shaped pattern inwhich a conductive body to which respective electrodes are commonlyconnected is arranged close to one of drain signal lines which arearranged to sandwich the pixels, and another pixel electrode out of theseparate pixel electrode has a comb-teeth-shaped pattern in which aconductive body to which respective electrodes are commonly connected isarranged close to another drain signal line.
 4. A liquid crystal displaydevice according to claim 1, wherein the counter electrode of each pixelis electrically connected with the counter electrode of another pixelwhich is arranged close to each pixel with a gate signal line arrangedtherebetween through a conducive layer which is formed on an insulationfilm which is formed in a state that the insulation film also covers thegate signal line.
 5. A liquid crystal display device in which twoneighboring thin film transistors are provided to each pixel, whereinsemiconductor layers of the respective thin film transistors are formedin common, on upper surfaces of the semiconductor layers, respectivedrain electrodes of the respective thin film transistors are formed in astrip shape, are curved and are formed in an semicircular shape having acenter thereof on distal ends of source electrodes which constitutepairs with the drain electrodes, and the drain electrode of one thinfilm transistor is physically commonly connected with the drainelectrode of another thin film transistor at a position where the drainelectrodes are arranged close to each other, and a width of a commonlyconnected portion is equal to a width of portions other than thecommonly connected portion.
 6. A liquid crystal display device whichincludes a pixel electrode and a counter electrode in a pixel formed ona surface of a substrate which faces liquid crystal, the counterelectrode is formed below an insulation film, and the pixel electrode isformed above the insulation film, wherein the pixel electrode isconstituted of separate pixel electrodes to which a video signal whichis supplied to the pixel is inputted through separate thin filmtransistors at the same timing, the separate pixel electrodes arerespectively formed of a plurality of electrodes and the electrodes arealternately arranged, and the separate thin film transistors havesemiconductor layers in common, on upper surfaces of the semiconductorlayers, respective drain electrodes of the respective thin filmtransistors are formed in a strip shape, are curved and are formed in ansemicircular shape having a center thereof on distal end portions ofsource electrodes which constitute pairs with the drain electrodes, thedrain electrode of one thin film transistor is physically commonlyconnected with the drain electrode of another thin film transistor at aposition where the drain electrodes are arranged close to each other,and a width of a commonly connected portion is equal to a width ofportions other than the commonly connected portion.
 7. A liquid crystaldisplay device comprising: a first substrate and a second substratewhich are arranged to face each other with liquid crystal therebetween;a plurality of gate signal lines and a plurality of drain signal lineswhich are formed on the first substrate; pixels which are formed asregions which are surrounded by the plurality of gate signal lines andthe plurality of drain signal lines; counter electrodes formed on thepixels, an insulation film formed above the counter electrodes; andpixel electrodes formed above the insulation film; wherein the pixelelectrodes include a first pixel electrode and a second pixel electrodewhich are overlapped to the counter electrode in plane, the first pixelelectrode and the second pixel electrode are electrically connected withthe same drain signal line through separate switching elements, thefirst pixel electrodes and the second pixel electrodes respectivelyinclude a plurality of electrodes, and the electrodes which belong tothe first pixel electrode and the electrodes which belong to the secondpixel electrode are alternately arranged.
 8. A liquid crystal displaydevice according to claim 7, wherein the separate switching elements arecontrolled by the same gate signal line.
 9. A liquid crystal displaydevice according to claim 7, wherein the first pixel electrode has acomb-teeth-shaped pattern in which a conductive body to which theplurality of electrodes are commonly connected is arranged close to onedrain signal line of the pixel, and the second pixel electrode has acomb-teeth-shaped pattern in which a conductive body to which theplurality of electrodes are commonly connected is arranged close toanother drain signal line of the pixel.
 10. A liquid crystal displaydevice according to claim 7, wherein the counter electrode of each pixelis electrically connected with the counter electrode of another pixelwhich is arranged close to each pixel with a gate signal line arrangedtherebetween through a conducive layer which is formed on an insulationfilm which is formed in a state that the insulation film also covers thegate signal line.
 11. A liquid crystal display device in which twoneighboring thin film transistors are provided to each pixel, whereinsemiconductor layers of the respective thin film transistors are formedin common, on upper surfaces of the semiconductor layers, respectivedrain electrodes of the respective thin film transistors are formed in astrip shape, are curved and are formed in an semicircular shape having acenter thereof on distal end portions of source electrodes whichconstitute pairs with the drain electrodes, and the drain electrode ofone thin film transistor is physically commonly connected with the drainelectrode of another thin film transistor at a position where the drainelectrodes are arranged close to each other.